1. Field of the Invention
The present invention relates to an improved casting method and apparatus for producing a cast product of aluminum or the like, particularly preferable when a disintegratable core or a sand core is set into a mold at every casting shot.
2. Description of the Related Art
A cast product having an undercut portion or a cavity is generally prepared by a gravity casting machine, which is a casting machine having a relatively low pressure, or a low-pressure molding machine, while utilizing a sand core formed by solidifying a casting sand by a phenolic resin or the like. The low-pressure casting machine, however, is defective in that the casting cycle is long, the thickness of a cast product cannot be reduced, and it is difficult to stabilize the quality of the cast product. Recently, however, it has become possible to perform the casting, operation by a high-pressure casting machine by utilizing a disintegratable core such as a sand core, by which the melt is prevented from intruding into the core and the die casting method is improved.
The high-pressure casting machine is classified as a lateral casting system or a vertical casting system, according to the casting direction. The lateral casting system was a lateral die casting machine, and the casting machine used by the vertical casting system is classified as a vertical clamping type or a lateral clamping type.
The high-pressure casting machine of the vertical casting system gives especially excellent results in that, since the contact area between the metal and the melt cast in a casting sleeve is small, there is little reduction of the temperature of the melt and the intrusion of a gas into the casting sleeve is inhibited.
In the casting method and casting machine using a disintegratable core, the disintegratable core must be easily attached to the molds, the melt must run correctly during the casting operation, and defects such as blow holes formed by an intrusion of gas into a cast product and cavities such as ingot piping caused by solidification and contraction, must not be formed. The disintegratable core must not be broken during the casting operation, there must be no intrusion of the molten metal into the sand core, i.e., melt intrusion, the core must be easily removed after the casting operation, and no sand must remain on the cast product.
As pointed out hereinbefore, the high-pressure casting machine is classified as the lateral clamping type or the vertical clamping type, according to the clamping direction, and as the lateral casting system or the vertical casting system according to the casting direction.
In the lateral clamping type, since the melt is filled in the rising state in the cavity, there is less intrusion of gas than in the vertical clamping type during the casting operation, and since a gas vent formed on the parting face of the mold is not clogged before completion of the filling operation, casting defects such as blow holes do not occur.
In the vertical casting system, since the contact area between the metal and the melt cast in the casting sleeve is smaller than in the lateral casting system, there is less reduction of the temperature of the melt, and since the intrusion of gas does not occur in the injection sleeve during the casting operation, casting defects such as blow holes do not occur.
Accordingly, for the above-mentioned reasons, a high-pressure casting machine of the vertical casting system and lateral clamping type is most widely used as the high-pressure casting machine using a disintegratable core. Although a product having a high casting quality can be produced by this casting machine, the attachment of the disintegratable core to the molds is cumbersome, and particularly when the disintegratable core is supported by a movable core, since the disintegratable core must be suspended in the air, and thus is not precisely positioned, the disintegratable core can be easily broken by collision with the mold. Furthermore, when the skirt portion of the disintegratable core is inserted into the supporting portion of the mold, the sand constituting the skirt portion is eroded by rubbing on the mold and intrudes into the melt during the casting operation to form defects, and thus it is difficult to easily obtain a good product. Moreover, in principle, automation of the attachment of the disintegratable core is impossible.